The Chinese government killed or imprisoned 18 to 20 CIA sources in a two-year period, crippling US spying operations in Beijing.

The sources for the Central Intelligence Agency were jailed and killed from 2010 to 2012 and the origin of the breach has still not been identified, according to The New York Times.

Investigators remain divided over whether there was a spy within the CIA who betrayed the sources or whether the Chinese hacked the CIA’s covert communications system.

The Chinese government impaired US spying operations in China by killing or imprisoning 18 to 20 CIA sources from 2010 to 2012, according to a report by the New York Times. (Stock photo of Chinese soldiers)

The Chinese killed at least a dozen people providing information to the CIA from 2010 through 2012, dismantling a network that was years in the making, the Times said, citing current and former US officials.

One source was shot and killed in front of a government building in China, three officials told the newspaper, saying that was designed as a message to others about working with Washington.

The breach was considered particularly damaging, with the number of assets lost rivaling those in the Soviet Union and Russia who perished after information passed to Moscow by spies Aldrich Ames and Robert Hanssen. Ames was active as a spy in the 1980s and Hanssen from 1979 to 2001.

The CIA declined to comment when asked about the Times report on Saturday.

The Chinese activities began to emerge in 2010, when the American spy agency had been getting high quality information about the Chinese government from sources deep inside the bureaucracy, including Chinese upset by the Beijing government’s corruption, four former officials told the newspaper.

The information began to dry up by the end of the year and the sources began disappearing in early 2011.

As more sources were killed the FBI and the CIA began a joint investigation of the breach, examining all operations run in Beijing and every employee of the U.S. Embassy there.